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topic 1384

Help choosing Anodize Coating for Marine Environment?


We are working with a customer who mfg's a product which will be used in a marine environment - both salt & natural water. The product will also be part of a heating element, with temperatures reaching 300 degrees F in the element. The water shouldn't go over 90 degrees F or so.

Looking for info on what is the best anodic finish.

IE: Type III Hardcoat vs Conventional Type II, sealed vs unsealed & which seal is best Dichromate, Nickel, Hot Water.

Also, would any seals like Dichromate or Nickel have potential to leach out and cause harm to fish or marine life nearby?

Any help would be greatly appreciated.


David A. Kraft
- Long Island City, New York


I don't know the answers, David, I'm only chatting with you here, but--

Another anodizing shop wrote in letter 270 (in the archives on line here) about the fact that there are right aluminum alloys for this application.

300 degrees, immersed in 90 degree water, doesn't seem very hot to me, though I could be off track.

Dichromate seals are probably the best for corrosion resistance. Some paints have been outlawed for use of boats, but having just completed a little boating course, nobody mentioned chromates.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Q. Hello, We are starting a new venture in manufacturing shift knobs, etc. Will a thick layer of regular anodizing offer long life, or should we use hard anodizing? How much? Pieces will be proximately 1.5" x 4.5" 6061-t6 aluminum. Regards, Russell Warner P.S. Are there any other coatings that you would recommend?

Russell Warner
engineering - Solvang, California

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